Dear all,

Here are the results from the Be beam line windows heating by the beam:

beam,  spot size, Be DS window, Be US window
30 uA      5 mm   maxT_DS = 397 K, maxT_US = 396 K
30 uA  0.2 mm   maxT_DS = 425 K, maxT_US = 418 K
60 uA     5 mm   maxT_DS = 468 K, maxT_US = 463 K
60 uA 0.2 mm   maxT_DS = 531 K, maxT_US = 524 K

The Be US window is 0.254 mm thick, the DS window is 0.508 mm thick. The diameter of the US window is 3.7 cm, the DS window is 5.32 cm. Each Be window was assumed welded to an Al beam pipe and formed with a curvature of 7.25 cm in radius. The Be windows were assumed inside the N2 atmosphere generated by the jet cooling of the glass cell windows for beam, but with no specific jets aimed at them. The heat transfer mechanisms were: conduction through the Be material to the Al pipes, convection with the N2 gas on one side (vacuum on the other side) and radiative exchange with a 300 K background environment. 
The beam heating power was assumed to be 3 W in the US window and 6 W in the DS window at 30 uA, and double these numbers at 60 uA.

In conclusion: it seems that the Be windows should be able to take even up to 60 uA unrastered beam with an intrinsic diameter of at least 200 microns.

Steve: did you run a thermal and or stress analysis of the Be beam line windows?


Kind Regards,

Silviu